Summary

Despite the widely recognized practical importance of anticardiolipin
(aCL) ELISA, the reliability of this test has been recently discussed.
In order to investigate this area on European scale, we sent to 30 experienced
centers a questionnaire focusing on the diagnostic procedures
applied to patients with antiphospholipid syndrome (APS) and on the
detailed protocols used to perform aCL. Anticardiolipin ELISA was
found to be the most frequently performed test in patients with suspected
APS, but significant difference was shown among the various protocols.
The cross-laboratory multiple examination of ten serum samples
evaluated independently by the 24 centers pointed out the difficulty in
getting comparable results. Therefore a “consensus” protocol was derived
from the aCL methods giving the best performance. The materi-als
and reagents necessary to perform the “consensus” method, including,
as putative standards, one IgG and one IgM monoclonal antibody
(HCAL and EY2C9) were distributed to 19 Centers. The results of one
IgG and one IgM aCL high positive sera measured in serial dilutions
were compared. A progressive decrease in the variability of the values
obtained for a given sample appeared evident when all the laboratories
used the same standard, in their own in-house ELISA and even more in
the “consensus” ELISA.
Our data show that aCL ELISA standardization is necessary in order
to obtain comparable results in different laboratories.